I have a custy I have been cleaning man and beast for about ten years. Changed to wfp in 2006 and call monthly at £20 for a 30's 5 bed detached. Takes 30/40 mins. No payment probs. When not in I lift the gate off the hinges and do the back.
She has leaky seals on a set of patios which I blade.
She doesn't like wfp even tho' it does a good job and she makes a point every so often to have a moan. Examples.
"Leaves streaks on kitchen window" - actually on the insides.
"Some windows are misty" - broken down units.
"Wfp causes misty windows" - no, luv - 15 year old windows with broken down units cause misty windows.
So it goes on - but she pays and I clean and she pays and I clean and she pays etc. Always get a coffee or tea.
Anyhoo - cleaned on Friday and they were away on the weekend and came back on the Tuesday and I get a call.
Her - "You've charged me £20 but you haven't done the backs"
Me - "Yes I did the backs"
Her - "They're all marked with little mucky spots on one side of the house and I've got a new cleaner who does the insides and she says it's definitely on the outsides, the fronts are brilliant but the backs are filthy."
Me - "We have had three days of driving rain since I cleaned them and the wind picks up the muck from the Motorway and Avonmouth and marks the windows."
Her - "What about your rain guarantee?"
Me (
thinks: damn!) 
"Well that is for 24 hours and I might stretch to two days but its now 4 days since I cleaned them."
Her - "Well if you know it's going to rain it's hardly worth doing is it?"
Me - "Well if you take your car through the car wash and it rains on it two days later do you expect a freebie?"
Her "Speechless"
Anyhoo I went back and cleaned the backs "as she is a good custy" and it's the first time ever I've been called on my rain guarantee (even tho' I went out of the terms of the agreement for her).
So I've settled on strike one rather than drop.
Whajoofink?